Macedonian police have used tear gas and stun guns to repel a crowd of migrants who burst through a barbed-wire fence on the Greek border, where thousands have gathered over the past several days.

Several hundred Iraqi and Syrian refugees, angered by days of delays in crossing the border into Macedonia, used a steel pole as a battering ram to break open a gate at the Idomeni border crossing on February 29.

The refugees, including women and children, had earlier charged past Greek police to reach the gate, shouting, "Open the border!"

Greek authorities say the number of people massed at the border with Macedonia has exceeded 7,000 -- a buildup sparked by moves by Austria and several Balkan states to limit access to migrants coming from Greece.

Earlier in the day, Macedonian police allowed some 50 people in, after keeping the crossing sealed for eight hours, but closed it again after the clashes.

No arrests or injuries were reported in the clashes, and it was not clear how many people managed to get through.

Macedonia has said it will only allow as many people as accepted by Serbia, which is next on the migrants' route toward Western Europe.

This has led to a huge bottleneck in Greece, where authorities say more than 22,000 people are stuck and more are arriving every day.

Call For United Front

More than 1 million people have reached Europe over the past year -- mostly arriving in small smugglers' dinghies from Turkey on Greece's eastern Aegean Sea islands.

Greece has been left to cope with most of the burden of new arrivals since its Balkan neighbors and Austria imposed a cap on migrant numbers, with relations between Athens and Vienna souring dramatically.

Greece last week withdrew its ambassador to Vienna, while Austria's Chancellor Werner Faymann accused Greece of "behaving like a travel agency" for refugees.

Meanwhile, German Chancellor Angela Merkel has urged Europe to show a united front in helping Greece avoid "chaos."

"Does anybody seriously believe that all the euro states who last year fought all the way to keep Greece in the euro zone -- and we [Germany] were the strictest -- can one year later allow Greece to, in a way, plunge into chaos?"

Merkel also stood by her decision last year to allow refugees into Germany without a limit on numbers, saying she had no "Plan B."

In France, authorities the northwestern port city of Calais,on February 29 started dismantling a large refugee camp known as "The Jungle."

The camp, for years a temporary shelter for migrants trying to get to Britain, on the other side of the English Channel, has grown explosively over the past year amid Europe's migrant crisis.

The camp's precise population is unclear. Local officials say it houses 3,700 people, while British-based Help Refugees charity puts the number at 5,500.